Continuous process for the manufacture of esters



A. A. BACKHAU S.

CONTINUOUS PROCESS FOR THE MANUFACTURE OF ESTERS.

APPLICATION FILED AUGJ. 1918.

1,4003% Patented Dec. 20,, 11921 2 SHEETS- SHEET I- A. A. BACKHAUS.

CONTINUOUS PROCESS FOR THE MANUFACTURE OF ESTERS.'

APPLICATION FILED AUGJ, 1918.

Patented Dec. 2%, 1921..

2 SHEETS-SHEET 2.

earner ARTHUR A. BACKHAUS, 01E lBALTlIMORE, MARYLAND, ASSEQItflE 1'0 U. 8. Ir

'ALCQHQL CG A CQRPORATIQN OF WEST mantra.

CQHTHZUUUS PROCESS FOR THE MMHEDJFAGTURE UH ESTEREJ.

areas-re.

To all whom it may concern Be it known that ll, ARTHUR A. BAGKHAUS, of Baltimore, in the State of Maryland, have invented a certain new and useful lmroveinent in Continuous Processes for the Manufacture of Esters, and do hereby declare that the following is a full, clear, and exact description thereof.

My invention relates to a process by means of which esters may be made continuously, that is to say, without interruption, and has reference to the manufacture of many different kinds of esters in this way.

The object of my invention is to provide a process by means of which esters may be manufactured continuously, instead of requiring the repeated interruption of the process that was hitherto found necessary. A further object is to provide a process of this character by means of which esters, substantially entirely free from water, may be obtained. Further objects of my invention will appear from the detailed description contained hereinafter.

While my invention is capable of being carried out in many difierent ways, for the purpose of illustration 1 shall describe only certain ways of carrying out my invention hereinafter, and while it is capable of being carried out in connection with many different types of apparatus, 1 have shown only two types of apparatus for use in connection therewith in the accompanying drawings, in which- Figure 1 is a diagrammatic representa tion of an apparatus which may be used in accordance with my invention,

Fig. 2 is a diagrammatic representation of another type of apparatus which may be used in connection with my invention, and

Fig. 3 is an enlarged vertical section of a detail of one of the columns. I

Referring first to Fig. 1, 1 shall describe my invention as it is applied to the treatment of a weak acid, as for example, dilute acetic acid or vinegar with methyl alcohol in the production of methyl acetate, although it is to be understood that my process is applicable to the production of many different esters and from materials of many different strengths.

In the drawings, referring to the type illustrated in Fig. 1, I have shown a column specification of Letters Patent.

PatentedDec, an, rear,

.ttpplteation filed August if, 1918. serial lt'o. nearer.

carried by said plates 3, the adjacent plates being connected by overflow pipes 6. :1 preferably supply to the upper part of the column still 1 continuously a quantity of sulfuric acid having, for example, a strength of Be. to 66 B. lfhis is preferably done by means of a trapped pipe 7 leading from a sulfuric acid tank such as tank 8, shown as having its outlet controlled by a needle valve 9 and a sight feed 10. The sulfuric acid is preferably fed in the proportion of .83 parts by weight of sulfuric acid to 10 parts by Weight of vinegar having a stren h of 8% acetic acid, which vinegar is pre erably fed continuously to the still 1 by e. 9., a trapped pipe 11, leading from an acetic acid tank 12, shown as also provided with a needle valve 13 and a sight feed 14:. lln addition, methyl alcohol, preferably having a strength of approximately 95% is also fed, preferably continuously, but in the proportion of part by weight, and ordinarily through, c. 9., a trapped pipe 15 controlled by a needle valve 16 and a sight feed 17, leading from an alcohol tank 18. Initially, before feeding through the, pipes 10, 11 and 15, however, sufiicient methyl alcohol is preferably fed into the apparatus to seal all the pans in the column still 1. The proportion of alcohol is varied, however, according to the strength of the acetate, or the like, that is desired to be obtained. The still 1 is preferably heated at its lower end. by means such as a tubular heater 19 having inlet and outlet steam pipes 19 and 19 The effluent liquids such as water and sulfuric acid are preferably conducted away from the still 1 by a pipe 20 having a trap 21 therein. From the upper portion of the still 1 a vapor discharge pipe 22 is provided to conduct away the vapors such as the methyl acetate and alcohol, which may have a proportionate composition of 30 parts by weight of methyl acetate or like vapors to a second column 26 constructed in the same manner as the column 1, except that this column is not provlded with several inlets, and with the exception .5 that a trapped discharge pipe 27 preferably conveys away the methyl alcohol from the lower portion of said column 26 to the column 1 at a point which ma be opposite to the entry of the pipe 15. n the operation of the embodiment described the vapors from the pipe 25 ascend in the column 26 through'a descending current of methyl alco hol, and the vapors of methyl acetate containing a small amount of methyl alcohol, are conveyed by apipe 27 to a dephlegmator 28 from which the condensed methyl alcohol returns by a trapped pipe 29 to the top of the column 26,-while the vapors of methyl acetate are conducted by a pipe 30 to a condenser 31 from which the condensed methyl acetate is drawn off by a pipe 32. The methyl acetate produced in this manner is substantially water-free as shown by test with anhydrous copper sulfate.

In case it is desired to use a strong acid, as for example, glacial acetic acid, a somewhat difierent arrangement of apparatus may be used, as for example, an apparatus, such as shown in Fig. 2. The apparatus shownin Fig. 2 is constructed the same as the apparatus shown in Fig.1, except in the followin respects: In this instance, I-have provide a column 33 constructed the same as the column 1, except that there is only one trapped inlet pipe 34 which leads from a mixing tank 35 provided with a propeller 36 carried by a shaft 37, and rotated by a ulley 38 from any suitable source of power.

ulfuric acid may be, in this embodiment,

continuously fed to the tank 35 by means of a pipe 39 having a needle valve 40 and a sight feed 41 connected to a sulfuric acid tank 42. In this instance, the sulfuric acid is fed to the mixing tank 35in the proportion of, e. 9., 2 parts by weight of sulfuric acid having a strength of B. to 66 Be'., to 10 parts by weight of glaciaLacetic acid which is fed continuously to the tank 35 by means of a pipe 43 having a needle valve 44 and a sight feed 45 connected to an acetic acid tank 46. At the. same time methyl alcohol having a strength of 95 to 98% is continuously fed in the proportion of 6 parts by weight to the tank 35 by means of a pipe 4 having a needle valve 48 and a sight feed 49 connected to an alcohol tank 50. Initially, before feeding through the pipe 34, a quantity of methyl alcohol sufficient to fill the pans in the still 33 isintroduced by means of a valved pipe 50. In this instance, the reactionby which methyl acetate is formed takes place partly within the tank 35, although the reaction takes place in part also in the column 33. Said column 33 isas shown provided with a liquid outlet pipe, a,

vapor outlet pipe, alcohol return pipes, and

other connections just the same as in the the vapors of the ester, such as methyl acetate and methyl alcohol from the top of the column to the dephlegmator, from which the condensed water cai'rying some alcohol is returned to the top of the column to form liquid seals and to provide a descending body of methyl alcohol therein. The methyl acetate or like vapors, thus partly freed from methyl alcohol, may pass then to the second or rectifying column 26- in which nearly all of the methyl alcohol is removed and may be returned as a liquid to the column 1, while the esters, such as methyl acetate vapors containing a small amount of meth 1 alcohol pass out of the same into the deph 'egmator 28, from which point the remaining quantity of methyl alcohol is returnedto the column 26. The methyl acetate, or like vapors then pass to the condenser 31, from which the condensed acetate such as methyl acetate is continually drawn off.

In carrying out the process, the esterification is carried out more completely and more rapidly by reason of the continual removal by distillation of the ester from the esterification zone and because of the provision of much larger quantities of an ester such as methyl alcohol than are needed for the reaction. The quantity of methyl alcohol present is preferably four or five times the quantity of methyl alcohol required in the reaction. Furthermore, the smaller the percentage of the acetic acid in thedescending current of liquid in the still 1, which be comes weaker in the acid as it descends, the larger the quantity of methyl alcohol required to offset the difliculty of esterification, and, therefore, a large quantity of methyl alcohol is fed in at a point-where tus shown in Fig. 2 the sulfuric acid, the fatty acid such as glacial acetic. acid and the alcohol are preferably fed into the mixing tank 35 continually, in which tank the ester such as methyl acetate is partly formed, While the mixed liquids are drawn ofi" from said tank 35 by a single pipe 34 to the column still 33. Here, because of the strength of the fatty acid such as acetic acid, the reaction can be efiected to a large degree merely by mixing the reagents and this is done, therefore, in the tank 35, so as to relieve the still 33 correspondingly, in order to increase its capacity. in this instance, the remainder of the process may operate the same as in the case of the process used in the apparatus shown in Fig. 1.

By the term countercurrent in the claims, it is intended to cover the movement of acid and alcohol in opposite directions, either in the formof continuous streams or in the form of intermittent streams, such as streams or currents formed by the successive vaporization and condensation or absorption of one of the reacting materials in a manner to advance the relative position of any given particle of liquid.

It will be understood that other acids and other alcohols may be used instead of the methyl alcohol and, acetic acid, such for example, as formic acid and ethyl alcohol. Also crude pyroligneous acid may be used, as it contains acetic acid and methyl alcohol, etc. Also, instead of sulfuric acid another catalyst may be used, as a solution of niter cake, or hydrochloric, or any phosphoric acid, or organic acids, such as acetic acid in excess of the amount required in the ester formed.

While I have I described my invention above in detail, I wish it to be understood that many changes may be made therein without departing from the spirit thereof.

I claim:

1. The process of manufacturing esters comprising passing an organic acid in countercurrent to gradually increasing c0ncentrations of an alcohol, and in the presence of'a catalytic agent while distilling'oif the ester formed.

2. The process of manufacturing esters comprising passing an organic acid in countercur'rent to gradually increasing concentrations of an alcohol in the presence of a catalytic agent while continuously distilling 0d the esters and removing the water formed. 7

3. The process of manufacturing esters comprising passing an organic acid and a catalytic agent incountercurrent to increasing' concentrations of an alcohol while distilling 0d the ester formed.

4:."The process of manufacturing esters comprising passing an organic acid and a catalytic agent incountercurrent to increasing concentrations of an alcohol While continuously distilling off the ester formed, and removing the water.

alcohol in the distillate.

5. The process of manufacturing esters comprising flowing sulfuric acid and. an organic acid down a column still provided with plates in countercurrent to an alcohol, and distilling the ester formed from the top of the still.

6. The process of manufacturing esters comprising passing strong sulfuric acid and an organic acid down a column still provided with plates containing an alcohol, in countercurrent to an alcohol, continuously distilling off theester formed from the top of the still, and continuously removing the water formed from the bottom of the still.

7. The process of manufacturing esters comprising passing a strong catalytic agent and an organic acid down a column still provided with plates containing an alcohol in countercurrent to increasing concentrations of an alcohol, continuously distilling off the ester formed from the top of the still, and continuously removing the Water from the bottom of the still.

8. The process of manufacturing esters comprising passing an organic acid in countercurrent to gradually increasing concen trations of an alcohol in the presence of a catalytic agent while distilling oil the ester formed. and separating the ester from the 9. The process of manufacturing esters comprising passing an organic acid in countercurrent to gradually increasing concentrations of an alcohol in the presence of a catalytic agent while distilling off the ester formed, separating the ester from the alcohol in the distillate, and returning the alcohol to the still.

10. The process of manufacturing methyl acetate comprising passing acetic acid in countercurrent to gradually increasing concentrations of methyl alcohol in the presence of strong sulfuric acid while distilling off the methyl acetate formed.

11. The process of manufacturing methyl acetate comprising passing acetic acid in countercurrent to gradually increasing con-- centrations of methyl alcohol in the presence of strong sulfuric acid, continuously distilling off the methyl acetate formed, and

continuously removing the Water.

12. The process of manufacturing methyl acetate comprising passing acetic acid in and strong sulfuric acid down a column still provided with plates containing methyl alcohol, introducin methyl alcohol near the bottom of the sti l and heating the methyl alcohol near the bottom of the still in order to distil off the methyl acetate at the top of the still.

14. The process of manufacturing'methyl acetate comprising passing strong acetic acid and strong sulfuric acid down a column still provided with plates containing methyl alcohol, introducing methyl alcohol near the bottom of the still, heating the methyl alcohol near the bottom of the still in order to distil off the methyl acetate at the top of the still, purifying the methyl acetate by passing it through methyl alcohol and collecting the pure methyl acetate.

15. The process of manufacturing methyl acetate comprising passing strong acetic acid and strong sulfuric acid down a column still provided with plates containing methyl alcohol,continuousl replenishing said plates with methyl alco ol, heating the alcohol near the bottom of the still to expel the methyl acetate from the top thereof, passing said acetate vapors into a second still containing methyl alcohol, distilling off the methyl acetate from said second still, condensing methyl alcohol vapors from the acetate vapors, and recovering the purified methyl acetate.

16. The process of manufacturing methylacetate comprising continuousl passin strong a'cetlc acid and strong su fur1c aclc down a column still provided with plates containing methyl alcohol, continuously replenishing said plates with methyl alcohol as it is used up, heating the methyl alcohol near the bottom of the still to expel the methyl acetate from the to thereof, continuously removin aqueous liquid from the bottom of the still, continuously distilling off methyl acetate from the top and removing methyl alcohol therefrom, continuousl passing! the acetate vapors intoa second sti .1 near t e middle thereof, said still having plates containing methyl alcohol, heating the methyl alcohol niar the bottom of said second still to expel the meth l acetate from the top thereof continuous y passing the excess methyl alcohol from the bottom of the second still to the first still near its bottom, continuously separating methyl alcohol vapors from the methyl acetate 'va ors distilled off from the second still, an collecta ing the urified methyl acetate.

17. T e process which comprises forming an ester by feeding methyl alcohol, acetic acid and a catalytic agent to intermingleterials.

"18. The. process which comprises formin an ester by feeding methyl alcohol, glacia centrations, and in the presence of a cata- I lytic agent while distilling off the ester formed.

20. The process of manufacturing esters comprising allowing a current of an organic acid to react with successive quantities of an alcohol of progressively increasing concentrations in the presence of a catalytic agent while continuously distilling off the esters and removing the water formed.

21.'The process of manufacturing esters comprising allowing a current of an organic acid and strong sulfuric acid to react with successive quantities of an alcohol while flowing down a column-still provided with plates containing the alcohol, the alcohol on said plates increasing with concentration .toward the bottom of the still, and distilling oifllthe ester formed from the' top of the sti 22. The process of manufacturing esters comprising allowing a current of an organic acid to react with. successive quantities of an alcohol of progressively increasing concentrations in the presence of a catalytic agent while distilling off the ester formed, separating the ester from the alcohol in the disltiillate, and returning the alcohol to the sti 23. The process of manufacturing esters comprising allowing a current of an organic acid to react with successive separate quantities of an alcohol of rogressively increasing concentrations and in the presence of a catalytic agent while distilling off the ester formed.

24. The process of manufacturing esters comprising allowing a current of an organic acid to react with successive separate quantities of an alcohol of rogressively increasing concentrations in the presence of a catalytic agent while continuously distilling'ofi the esters and removing the -water formed.

25. The process of manufacturing esters comprising allowing a current of an organic acid to react with successive separate quantities of an alcohol of progressively increasing concentratlons in the presence of a catalytic agent while distilling off the ester formed, separating the ester from the alcohol in'the distillate, and returning the alcohol to the still. 7

26. The process of manufacturing esters comprising introducing an organic acid and a catalytic agent into a column still, intro-- ducing an alcohol into the still, and heatducing an alcohol into the still below the ing the latter to 'distil therefrom the ester point of introduction of the acid, and heatformed. 7 'ing the still near the point of introduction 15 27. The process of manufacturing esters of the alcohol in order to vaporize the latter 5 comprising introducing an organic acid and and distil oif from the still the ester formed. a catalytic agent into a'column still, intro- In testimony that I claim the foregoing dihcling Sub alcohol hneiu' the bottogn 1;)f thf and have hereunto set my hand. st' an eatin t e ower arto t est a v to distil therefi om the esteE- formed. ARTHUR BAOKHAUS' 1 0 28. The process of manufacturing esters- Witnesses:

comprising introducing an organic acid and E. J. WINTER, a catalytic agent into a column still, intro- 'J. B. JonNsoN. 

